The present invention is directed to the objective of providing a low-cost but highly accurate load cell capable of measuring small forces to a high degree of accuracy. One application for such a device is in food packaging, wherein the quantity of food products which are industrially packaged must very closely equal the labeled weight. For example, the packager may specify that a five pound package must be accurately weighed within 0.02 percent, i.e., within 1/1000 of a pound.
Furthermore, it is desirable for protection of such a precise system that it be able to withstand substantial overloading in any direction, and that its accuracy not be adversely affected by forces acting upon it in directions other than the normal vertical axis of measurement. It is essential to attenuate or divert extraneous forces or moments around the measuring element so that the sensing element itself can be designed to optimize its response to the desired force input. In this manner, other structural elements can be designed to safely carry the extraneous or overload forces. Such a system is preferable to the use of complex electrical compensating networks, which increase the cost of the unit and also decrease its reliability.
One prior art load cell having a resemblance to portions of the novel transducer disclosed herein is that shown in U.S. Pat. No. 3,994,161. However, the present transducer has improved sensitivity to the load to be measured, improved protection for overload and improved insensitivity to extraneous forces.